With the development in communication technology, a terminal such as a smartphone that has a communication function is in widespread use. Meanwhile, societal demands on reducing power consumption of terminals are increasing due to concern for global warming. Further, for a battery-powered terminal such as a smartphone, there is a need for reducing power consumption of the terminal from the standpoint of the convenience by increasing run time thereof.
In response to the demands for reducing power consumption, a framework named ACPI (Advanced Configuration and Power Interface) for power supply control is being proposed. According to the above, a state named “S3” is defined. The “S3” is a state that is called “Suspend to RAM.” In the “S3” state, values in registers of a CPU are written out in a main memory, and feeding of power to the CPU, a bus, and a bus device is stopped while the main memory is kept in an energized state. A terminal in the “S3” state cannot carry out an operation, but power consumption thereof is smaller than in an “S0” state (an operating state). Further, when the terminal returns to the “S0” state from the “S3” state, the terminal can return to a state prior to transitioning to the “S3” state. Therefore, it is more convenient than a cold boot.
Further, as another related technique, the following can be cited. Suppose a user logs on to a remote terminal from a local terminal via telnet and carries out operations such as text creation or the like on the remote terminal. At this time, if the local terminal transitions to the “S3” state from the “S0” state, a TCP (Transmission Control Protocol) connection pertaining to the telnet session is disconnected by the remote terminal. Thus, when the local terminal returns to the “S0” state from the “S3” state, a problem occurs in that a text that has been created on the remote terminal is lost, and further, a problem occurs in that the user must operate to again log on to the remote terminal. The aforementioned another related technique is intended to solve these problems. That is, as the local terminal transmits a “TCP-SLEEP” message to the remote terminal when having transitioned to the “S3” state, the TCP connection is prevented from being disconnected by the remote terminal.
Further, according to another related technique, in a case where there is no receiving or transmitting packet for a predetermined period of time in a wireless LAN terminal, information that is necessary to transmit data to a connected access point is stored in the terminal, and feeding of power to a communication circuit is stopped. When a transmitting packet is generated, power is fed to the communication circuit, and the packet is transmitted to the access point having been connected to previously using the stored information without carrying out a connecting procedure. In this way, by omitting the procedure to connect to the access point, a delay that is required for transmitting a packet after power is fed to a communication unit is reduced.
In recent years, services called Web services or cloud services have been in widespread use. For example, Gmail by Google Incorporated or the like can be cited. With Gmail, mail data are present on a server, and by accessing them from a Web browser, a list of received mail and content of selected mail are displayed without using a dedicated mail application. In a case where such a service is assumed, it is desirable from the standpoint of reducing power consumption that, each time the local terminal receives necessary data, the local terminal disconnects a TCP connection and stops feeding power to a communication section of the local terminal. For example, after received mail list data are acquired, the TCP connection is disconnected, and a received mail list screen is displayed. While a user is browsing through the received mail list screen, a control is carried out to stop feeding of power to the communication section. Then, when the user operates on the received mail list screen, power is fed to the communication section, and a TCP connection to a server is established. A request in accordance with that operation is then transmitted to the server, a response included in the response is received, and a screen is displayed using data included in that response.
However, if a TCP connection is reestablished each time a browser displaying the received mail list screen is operated in this way, a delay until a next screen is displayed on the browser increases due to overhead by a connection setup and a flow control called a slow start. Through this, convenience for the user decreases. This problem and a solution therefor are not described in the aforementioned another related technique. Further, in the aforementioned another related technique, since the entire local terminal stops operating in a power saving state (for example, “S3”), the user cannot operate the terminal in the power saving state, and thus there exists a problem in that the convenience is lost.
In addition, in the aforementioned yet another related technique, since an association with a wireless LAN access point is disconnected, the TCP connection is disconnected from the server. Accordingly, a problem that arises due to reestablishing a TCP connection cannot be solved.